The present application is based on and claims priority from Japanese Patent Applications: Hei 11-242528, filed Aug. 30, 1999 and Hei 11-247264, filed Sep. 1, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of obtaining information that corresponds to the Rxe2x80x94R interval of the electrocardiogram of a human body for medical and health examinations.
2. Description of the Related Art
The electrocardiogram has been used for medical and health examinations. Particularly, the Rxe2x80x94R intervals of the electrocardiogram have been frequently used to examine the heart beat rhythm and the automatic nervous system. The R-R intervals of the electrocardiogram are obtained from intervals of peak values of the R-wave that are most significantly observed in the QRS group, which is caused by depolarization of the ventricle.
On the other hand, it is considered to utilize the peak intervals between the pulse wavers peak values of the human-body as the information that corresponds to the Rxe2x80x94R intervals of the electrocardiogram.
Because the peak values of the pulse-waves are not so clear as the peak values of the R-wave, it has been difficult to accurately determine the peak intervals of the pulse-wave.
A commonly used pulse-wave sensor measures a pulse-wave of a human body by means of light absorbing characteristics of hemoglobin of the blood. Such a pulse-wave sensor includes a light-emitting element for emitting light to a finger and light sensing element for sensing the light reflected from the finger.
While such a pulse-wave sensor is attached to a human finger, the sensor always moves as the human body moves. This motion causes noises, which are included in the pulse-wave data. In particular, when a shoulder or an elbow moves, the quantity of the blood changes, thereby causing noises. It has been also difficult to eliminate, from such a pulse-wave sensor, noises caused by outside light such as sunshine or light of lamps.
Therefore, a main object of the invention is to provide an improved method of measuring pulse-waves that is effective to provide practically accurate information that can be substituted for the Rxe2x80x94R intervals of the electrocardiogram.
According to a main feature of the invention, a method of obtaining information that corresponds to the Rxe2x80x94R interval of electrocardiogram from the pulse-wave of a human body is comprised of differentiating the pulse-wave to provide a speed-pulse-wave (differentiated pulse-wave), and measuring the intervals of peaks of the speed-pulse-wave. The intervals of peaks of the speed-pulse-wave practically approximate the Rxe2x80x94R interval of the cardiogram.
In the meantime, the bottom interval of the pulse waves corresponds to the interval between consecutive times when the speed-pulse-wave changes from a negative to a positive. While, the peak interval of the pulse-waves corresponds to the interval between consecutive times when the speed-pulse-wave changes from a positive to a negative.
Another object of the invention is to provide a method of measuring a pulse-wave that can detect noises included in the pulse-wave data.
According to another feature of the invention, a method of measuring a pulse-wave is comprised of differentiating the pulse-wave to provide a speed-pulse-wave, detecting peak values of the speed-pulse-wave, calculating the dispersion of said peak values and comparing the dispersion with a predetermined value to determine whether a noise is included in the pulse-wave or not.